Graber, Doris A., author
Congressional Quarterly Press, 1980
Buku Teks
Schmidt, Steffen W., author
Wadsworth, 2009
Buku Teks
Starling, Grover, author
The Dorsey Press, 1982
Buku Teks
McKenna, George, author
McGraw-Hill, 1998
Buku Teks
Shea, John C.
St. Martin's Press, 1984
Buku Teks